Among various semiconductor devices, power devices for high-power control that are used to control electric vehicles, electric automobiles and the like, generate a large amount of heat. Thus, as a substrate mounting such power devices, a power module substrate in which a metal plate having excellent conductivity and served as a circuit layer and metal layer is bonded on both surfaces of a ceramic substrate (insulation layer) composed of for example AlN (aluminum nitride) or the like, is conventionally widely used.
A semiconductor device as a power device (electronic component) is mounted on the circuit layer of such power module substrate via a solder material, and a power module is produced. In addition, a heat sink is bonded under the metal layer, and it has a structure in which the heat is allowed to be dissipated.
Conventionally, as a method for bonding a power module substrate and a heat sink together, for example, as shown in Patent Document 1, a method in which grease is interposed between a metal layer of a power module and a heat sink and they are clamped with screw is disclosed. Also, as shown in Patent Document 2, a method in which a metal layer of a power module substrate and a heat sink is bonded together via a solder is disclosed.